From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Add a way to keep ref counts on accesses to instances. This way, another
structure can hold a reference to an instance, and if the user frees that
instance, it wont be freed until the other structure frees it.
That is, if we create a structure called tracefs_hist, that takes an
instance on its creation. It can hold a reference to that instance, and
make sure that it does not get freed:
instance = tracefs_instance_create("my_instance");
hist = tracefs_hist_alloc(instance, "sched", "sched_wakeup", "pid", 0);
tracefs_instance_free(instance);
tracefs_hist_start(hist);
[..]
tracefs_hist_free(hist);
Will not crash, as the tracefs_instance_free() will not free the instance
as there's still a reference on it, and tracefs_hist_start() will still
have that reference. But then when the tracefs_hist_free() is called, then
the instance will get freed.
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
include/tracefs-local.h | 4 +++
src/tracefs-instance.c | 56 ++++++++++++++++++++++++++++++++++-------
2 files changed, 51 insertions(+), 9 deletions(-)
diff --git a/include/tracefs-local.h b/include/tracefs-local.h
index 512f17a7c812..2324dec9d076 100644
--- a/include/tracefs-local.h
+++ b/include/tracefs-local.h
@@ -25,6 +25,7 @@ struct tracefs_instance {
char *trace_dir;
char *name;
pthread_mutex_t lock;
+ int ref;
int flags;
int ftrace_filter_fd;
int ftrace_notrace_fd;
@@ -41,6 +42,9 @@ static inline pthread_mutex_t *trace_get_lock(struct tracefs_instance *instance)
return instance ? &instance->lock : &toplevel_lock;
}
+void trace_put_instance(struct tracefs_instance *instance);
+int trace_get_instance(struct tracefs_instance *instance);
+
/* Can be overridden */
void tracefs_warning(const char *fmt, ...);
diff --git a/src/tracefs-instance.c b/src/tracefs-instance.c
index 11fb580456ff..185d968ae319 100644
--- a/src/tracefs-instance.c
+++ b/src/tracefs-instance.c
@@ -20,7 +20,11 @@
#include "tracefs.h"
#include "tracefs-local.h"
-#define FLAG_INSTANCE_NEWLY_CREATED (1 << 0)
+enum {
+ FLAG_INSTANCE_NEWLY_CREATED = (1 << 0),
+ FLAG_INSTANCE_DELETED = (1 << 1),
+};
+
struct tracefs_options_mask toplevel_supported_opts;
struct tracefs_options_mask toplevel_enabled_opts;
@@ -79,15 +83,30 @@ error:
return NULL;
}
-/**
- * tracefs_instance_free - Free an instance, previously allocated by
- tracefs_instance_create()
- * @instance: Pointer to the instance to be freed
- *
- */
-void tracefs_instance_free(struct tracefs_instance *instance)
+
+__hidden int trace_get_instance(struct tracefs_instance *instance)
{
- if (!instance)
+ int ret;
+
+ pthread_mutex_lock(&instance->lock);
+ if (instance->flags & FLAG_INSTANCE_DELETED) {
+ ret = -1;
+ } else {
+ instance->ref++;
+ ret = 0;
+ }
+ pthread_mutex_unlock(&instance->lock);
+ return ret;
+}
+
+__hidden void trace_put_instance(struct tracefs_instance *instance)
+{
+ pthread_mutex_lock(&instance->lock);
+ if (--instance->ref < 0)
+ instance->flags |= FLAG_INSTANCE_DELETED;
+ pthread_mutex_unlock(&instance->lock);
+
+ if (!(instance->flags & FLAG_INSTANCE_DELETED))
return;
if (instance->ftrace_filter_fd >= 0)
@@ -108,6 +127,20 @@ void tracefs_instance_free(struct tracefs_instance *instance)
free(instance);
}
+/**
+ * tracefs_instance_free - Free an instance, previously allocated by
+ tracefs_instance_create()
+ * @instance: Pointer to the instance to be freed
+ *
+ */
+void tracefs_instance_free(struct tracefs_instance *instance)
+{
+ if (!instance)
+ return;
+
+ trace_put_instance(instance);
+}
+
static mode_t get_trace_file_permissions(char *name)
{
mode_t rmode = 0;
@@ -248,6 +281,11 @@ int tracefs_instance_destroy(struct tracefs_instance *instance)
if (path)
ret = rmdir(path);
tracefs_put_tracing_file(path);
+ if (ret) {
+ pthread_mutex_lock(&instance->lock);
+ instance->flags |= FLAG_INSTANCE_DELETED;
+ pthread_mutex_unlock(&instance->lock);
+ }
return ret;
}
--
2.30.2
|